Run the STM Demonstrator and do every step exactly as shown! on the pictures below. Once the board is in bootloader mode, you can start with the flashing. This can be done by connecting the SBL pad with the 3.3V while powering on the board. To flash the firmware, the flight controller must be in bootloader mode. Then downloaded the Cleanflight firmware for the OpenPilot CC3D board from here.
You can download the latest version from the STM website. I also installed the STM Flash Demonstrator. Connecting the CC3D flight controller with the FTDI as usual, 5V, GND, TX and RX to the MainPort on the CC3D. What do you need to flash the Cleanflight firmware on the CC3D board: basically an FTDI adapter or an Arduino with FDTI chip on it, such my Arduino Nano v3. I decided to erase the old one and use just the Cleanflight. Even more: you can have both firmwares OpenPilot and Cleanflight installed on the board. You can find more information about Cleanflight on its website. This is another 32bit version of the MultiWii firmware, exactly as Baseflight is. It is possible to do this by installing the Cleanflight firmware. I found this forum page on the OpenPilot website. So I decided to look if it is possible to use the Baseflight firmware on the CC3D board, as both flight controllers are so identical. There are simply too much options in GSC, which is good, but it is a bit complicated for a beginner (this is my personal opinion).
I tested the original software OpenPilot GCS and it looks very good, but I still like the Baseflight solution using Google Chrome and its minimalistic design. If using the newest Cleanflight firmware there is benefit from the flash: the Blackbox feature saves flight data on it and you can check it later on your PC. There is something more on the CC3D compared to the Acro Naze32: 16MBit Flash Chip 25P16VP. On the OpenPilot CC3D there are JST 1mm ports used. I also prefer the pins on the Naze32 for connecting GPS or receiver. Personally I find the Micro-USB better, as I always have such cable on my desk for charging my phone. The Naze32 has a Micro-USB and the CC3D a Mini-USB port. Both use a 32bit STM processor, has the same MPU6000 sensor and are 36x36mm boards. The Naze32 and CC3D are very similar to each other. Update: well it is much cheaper now and keeps going down. The quality is good in my opinion, all SMD parts are soldered as it should be. In about 2 to 3 weeks the flight controller arrived here in Germany. So I went to Aliexpress and bought one with case for 18,99$ including shipping.
Well, the price of almost 32 $ plus 4 $ shipping cost from HobbyKing was too much for me, considering the Naze32 with the same processor and MPU6050 sensor is about 24$. I also wanted to try this flight controller, especially since Nick (the developer of the AUAV-X2 flight controller) recommended it. I mentioned that HobbyKing started to sell the OpenPilot CC3D board in late September. Flying my SG Adventure Mini was just great. The firmware (Baseflight) and settings were easy to set up through Google Chrome browser. I bought myself a Naze32 Acro from HobbyKing back in September last year and I was impressed by the tiny flight controller. Many people who a starting with the multicopters or just want to try another flight controller ask this question: should I buy OpenPilot CC3D or Naze32?